Theoretical studies on the kinetics and mechanism of the gas-phase reactions of CHF2OCHF2 with OH radicals

The mechanism, kinetics and thermochemistry of the gas-phase reactions between CHF2OCHF2 (HFE-134) and OH radical are investigated using the high level ab initio G2(MP2) and hybrid density functional model MPWB1K quantum chemical methods. Two relatively close in energy conformers are found for CHF2OCHF2 molecule; both of them are likely to be important in the temperature range (250-1000 K) of our study. The hydrogen abstraction pathway for both the conformers with OH radical is studied and the rate constants are determined for the first time in a wide temperature range of 250 - 1000 K. The G2(MP2) calculated total rate constant value of 2.9 x 10(-15) cm(3) molecule(-1) s(-1) at 298 K is found to be in very good agreement with the reported experimental value of 2.4 x 10(-15) cm(3) molecule(-1) s(-1) at 298 K. The heats of reaction for CHF2OCHF2 + OH reaction is computed to be -13.2 kcal mol(-1). The atmospheric lifetime of CHF2OCHF2 is expected to be around 12 years.